Wait Type LCK_M_SCH_M_ABORT_BLOCKERS

Wait statistics, in the context of SQL Server, refer to the amount of time that a query spends waiting to access data in the database. When a client application requests data from the database, the request is placed in a queue and the client application must wait for its turn to access the data. The time that the query spends waiting is called a "wait" and is tracked by SQL Server. This information can be used to identify potential performance bottlenecks and optimize the performance of the database. Wait statistics are commonly used by database administrators to diagnose and troubleshoot performance issues in SQL Server.

SQL Server uses locks to ensure consistency and manage concurrency during transactions and schema modifications. Sometimes, these locks lead to waits, such as the LCK_M_SCH_M_ABORT_BLOCKERS wait type. Understanding this wait type helps in identifying and resolving performance bottlenecks related to schema changes in your SQL Server environment.

What is LCK_M_SCH_M_ABORT_BLOCKERS?

The LCK_M_SCH_M_ABORT_BLOCKERS wait type occurs when a session is waiting to acquire a Schema Modification (SCH_M) lock but is blocked by another transaction. An SCH_M lock is used when making schema changes to database objects, such as altering a table or creating an index. The “Abort Blockers” component indicates that SQL Server must wait for the blocking transactions to either complete or be aborted before granting the lock.

In simpler terms, this wait type means SQL Server is delaying a schema modification to prevent conflicts with other active transactions that are interacting with the affected object.

Why Does LCK_M_SCH_M_ABORT_BLOCKERS Happen?

Several factors can lead to LCK_M_SCH_M_ABORT_BLOCKERS waits, including:

• Ongoing transactions holding locks on the object being modified.
• High contention for specific database objects undergoing schema changes.
• Concurrent operations such as queries or updates on the object in question.
• Long-running transactions, causing delays in releasing locks.
• Schema changes attempted during peak usage times.

Addressing these factors can reduce contention and allow schema modifications to proceed more smoothly.

How to Monitor LCK_M_SCH_M_ABORT_BLOCKERS Waits

Monitoring LCK_M_SCH_M_ABORT_BLOCKERS waits is essential to diagnosing their causes and mitigating their impact. The Database Health Monitor provides an effective solution for tracking this wait type. Its Historic Waits Monitoring feature gives you detailed insights into when these waits occur, their duration, and how they affect your SQL Server environment.

Using Database Health Monitor, you can identify patterns in these waits and determine whether they are caused by blocking chains, resource contention, or workload inefficiencies. This data allows you to take targeted actions to resolve issues and optimize your database operations.

What Can You Do About LCK_M_SCH_M_ABORT_BLOCKERS Waits?

If you experience frequent or prolonged LCK_M_SCH_M_ABORT_BLOCKERS waits, consider implementing these strategies:

• Analyze blocking chains with tools like Activity Monitor or Extended Events to identify and resolve conflicting transactions.
• Schedule schema modifications during maintenance windows or off-peak hours to minimize conflicts with active workloads.
• Optimize long-running transactions to reduce their execution time and release locks sooner.
• Coordinate schema changes with other teams to avoid overlapping operations on the same objects.
• Test schema modifications in a non-production environment to identify potential conflicts before applying them to production.
• Use tools such as transactional replication or partition switching to reduce the impact of schema modifications on production workloads.

Implementing these steps can help you reduce contention and ensure smoother schema modifications in your SQL Server environment.

Why Use Database Health Monitor?

The Database Health Monitor is an invaluable tool for tracking SQL Server wait types, including LCK_M_SCH_M_ABORT_BLOCKERS. Its Historic Waits Monitoring feature provides actionable insights into wait trends, helping you identify and resolve performance bottlenecks. With Database Health Monitor, you can maintain a high-performing and reliable SQL Server environment.

Start using Database Health Monitor today to monitor and optimize your SQL Server’s performance, ensuring reliable and efficient database operations!

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Applies to

Related Waits

See Also

• More About LCK_M_SCH_M_ABORT_BLOCKERS